arXiv subjects

Vlad C. Coroamă

Publications and source records attributed to Vlad C. Coroamă.

5 recordsLinked to original sources

arXiv2026

Circular Economy Synergies and Trade-offs in Data Centres

This report analyses data centre (DC) sustainability and circularity, revealing existing synergies and trade-offs: The PUE is too coarse, mixing cooling and power provisioning. It wrongly attributes server fan consumption and transformation losses to IT energy. It does not measure compute but infrastructure efficiency, which is already outstanding. Compute energy, however, is exploding. Better energy metrics for DCs would thus cover i) compute efficiency, ii) transformation efficiency, and iii) cooling overhead. Trade-offs exist between cooling energy and water as well as on-site and upstream water: Consuming water on-site lowers the cooling energy, which also lowers the water consumed upstream in power generation. For 'wet' electricity, there is little competition: It is worth spending more on-site energy to save both electricity and related upstream water. For 'dry' electricity, there is a trade-off. Waste heat recovery brings energy circularity but has limited uses and is not the same energy quality, a fact not reflected by current metrics. A better metric would consider the avoided energy through heat recovery instead of the amount recovered. Material circularity can be achieved by interpreting the 9R framework in the context of DCs. Circularity-enhancing measures can be categorised into product design, process design and business models, choice of materials, and operating conditions. Together, they have effects across all circularity levels. The relation between DCs and the power grid is complex. Modern DCs present new challenges for the grid. Mitigation includes battery storage and onsite generation. These measures have, in turn, further consequences, both beneficial and detrimental. They can offer grid flexibility as well as innovations in the field of energy. But they also bring noise, pollution, and GHGs, and compete with the energy sector for resources.

cs.OH↗

arXiv2025

Temperature Optimisation in Data Centres

Raising server inlet temperatures tends to increase the server power consumption due to heightened server fan activity needed to compensate for the warmer air, and to decrease cooling infrastructure power consumption due to less intense and possibly less frequent chiller activity. Relying on primary data from two data centres of a colocation provider in Switzerland, this study succeeds in confirming and quantifying the first effect: In the upper half of the ASHRAE recommended temperature range and slightly above it, i.e., between 23 - 30 °C, the server power consumption correlated positively with the temperature, with a server room-wide temperature sensitivity of 0.35 - 0.5 %/°C. Based on the available data and due to ambivalent results, the study did not succeed in answering which effect is stronger for the entire data centre: the increase in server consumption or the savings in cooling consumption. Whether raising inlet temperatures beyond the ASHRAE upper limit (i.e., 27 °C) yields additional overall benefits thus remains an open question that would be best addressed through controlled experiments. A few pieces of evidence indicate nevertheless that the upper part of the current ASHRAE recommendation (i.e., around 25 - 27 °C) might be the current sweet spot for colocation DCs. The widely used power usage effectiveness (PUE) metric is not at all useful in this context. For practical reasons but semantically wrong, the server fan power consumption is included in the consumption of servers (and thus, of the IT infrastructure) and is thus on the wrong side of the PUE fraction. An inlet temperature raise, which will lead to increased fan consumption, will thus always yield a PUE decrease, irrespective of what happens to the overall data centre power consumption.

cs.OH↗

arXiv2025

How Viable are Energy Savings in Smart Homes? A Call to Embrace Rebound Effects in Sustainable HCI

As part of global climate action, digital technologies are seen as a key enabler of energy efficiency savings. A popular application domain for this work is smart homes. There is a risk, however, that these efficiency gains result in rebound effects, which reduce or even overcompensate the savings. Rebound effects are well-established in economics, but it is less clear whether they also inform smart energy research in other disciplines. In this paper, we ask: to what extent have rebound effects and their underlying mechanisms been considered in computing, HCI and smart home research? To answer this, we conducted a literature mapping drawing on four scientific databases and a SIGCHI corpus. Our results reveal limited consideration of rebound effects and significant opportunities for HCI to advance this topic. We conclude with a taxonomy of actions for HCI to address rebound effects and help determine the viability of energy efficiency projects.

cs.HC↗

arXiv2020

A Methodology for Assessing the Environmental Effects Induced by ICT Services. Part II: Multiple Services and Companies

Information and communication technologies (ICT) can make existing products and activities more efficient or substitute them altogether and could thus become crucial for the mitigation of climate change. In this context, individual ICT companies, industry organizations and international initiatives have started to estimate the environmental effects of ICT services. Often such assessments rely on crude assumptions and methods, yielding inaccurate or even misleading results. The few existing methodological attempts are too general to provide guidance to practitioners. The starting points of this paper are i) a high level standard from the European Telecommunication Standardisation Institute (ETSI) and the International Telecommunication Union (ITU), and ii) its suggested enhancements for single service assessment outlined in "A Methodology for Assessing the Environmental Effects Induced by ICT Services Part I: Single services" (Part I in short). Building on the assessment of single services, the current article identifies and addresses shortcomings of existing methodologies and industry practices with regard to multiple services assessment. For a collection of services, it addresses the goal and scope definition, the so far ignored aggregation of effects among several services, and the allocation between several companies contributing to one or more services. The article finally brings these considerations together with those of Part I into a workflow for performing such assessments in practice.

cs.CY↗

arXiv2020

A Methodology for Assessing the Environmental Effects Induced by ICT Services. Part I: Single Services

Information and communication technologies (ICT) are increasingly seen as key enablers for climate change mitigation measures. They can make existing products and activities more efficient or substitute them altogether. Consequently, different initiatives have started to estimate the environmental effects of ICT services. Such assessments, however, lack scientific rigor and often rely on crude assumptions and methods, leading to inaccurate or even misleading results. The few methodological attempts that exist do not address several crucial aspects, and are thus insufficient to foster good as-sessment practice. Starting from such a high level standard from the European Telecommunication Standardisation Institute (ETSI) and the International Telecommunication Union (ITU), this article identifies the shortcomings of existing methodologies and proposes solutions. It addresses several aspects for the assessment of single ICT services: the goal and scope definition (analyzing differences between ICT substitution and optimization, the time perspective of the assessment, the challenge of a hypothetical baseline for the situation without the ICT solution, and the differences between modelling and case studies) as well as the often ignored influence of rebound effects and the difficult extrapolation from case studies to larger populations.

cs.CY↗